Chemical mortar compositions and dowel compositions based on free radical-curing reaction resins have long been known. These reaction resins, as a rule, are composed of a curable resin component and a curing agent component. The curable resin component comprises, for example, a reactive polymer as well as a monomer capable of cross-linking, which is also referred to as a reactive diluent and serves to adjust the viscosity of the mortar composition and, by reaction during the curing, participates in the consolidation of the material, as well as fillers and conventional additives.
For example, DE 32 26 602 A1 describes a curable two-component mortar composition, which contains an unsaturated polyester resin, a reactive diluent, fillers, a thixotropic agents and a free radical-curing catalyst. In this connection, styrene or divinyl benzene is used as a reactive diluent.
The object of DE 36 17 702 A1 is a curable agent for fastening dowels and anchor rods and contains a curable acrylate, which, in addition to an organic peroxide curing agent, an accelerator, a desensitizing agent, mineral fillers and thixotropic agents, contains a reactive diluent. As reactive diluent, styrene, divinyl benzene, allyl esters of multibasic acids, methyl methacrylate, isopropyl methacrylate and isobutyl methacrylate are mentioned.
The DE 39 40 309 A1 also describes a mortar composition for fastening anchor rods in solid accommodating materials, the mortar composition containing free radical-curable vinyl ester urethane resins and a reactive diluent as optional component. Styrene, divinyl benzene, acrylates and the methacrylates are also mentioned as reactive diluents in this publication.
The DE 42 31 161 A1 also discloses a two-component mortar for fastening anchor rods in boreholes, the mortar containing hydraulically setting and/or polycondensable compounds as inorganic, curable compounds and curable vinyl esters as organic curable compounds. As reactive diluents, monofunctional and polyfunctional acrylate and methacrylate esters are named according to the teachings of this state of the art.
Finally, in the DE 41 31 457 A1, a two-component mortar composition for fastening anchor rods, dowels and screws in boreholes chemically is described. It contains a free radical-curable vinyl ester resin or vinyl urethane resin and, spatially separated therefrom, a curing agent for the resin, as well an acetoacetoxyalkyl (meth)acrylate as comonomer for achieving good adhesion to silicatic materials.
With the help of the last-mentioned styrene-free chemical fastening system, it has become possible to optimize the reaction resins specifically for certain substrates by the selection of reactive diluents. Accordingly, it has turned out that good wetting, polar, low viscosity monomers, such as hydroxyalkyl methacrylates, are suitable for achieving good adhesion to substrates of concrete. On absorptive substrates, such as bricks and roofing tiles which, moreover, contain appreciable amounts of iron ions, which interfere with the free radical curing with diacyl peroxides, the use of less polar monomers of higher viscosity, such acetoacetoxyalkyl (meth)acrylates, has proven its value. These monomers have proven to be suitable for forming chemical fastening systems, which are designed for solid brick and hollow brick substrates.
Although it is known that two-component mortar compositions may be adapted to specific substrates by the appropriate selection of reactive diluents, it has turned out, on the other hand, that these mortar compositions exhibit appreciable weaknesses on other substrates and do not permit the necessary adhesion to be achieved. Accordingly, it was discovered by the inventors that the performance of a two-component mortar composition, which contains hydroxyalkyl methacrylates, such as hydroxyethyl methacrylate or hydroxypropyl methacrylate as reactive diluent, suffers drastically on bricks, because these reactive diluents evidently penetrate rapidly into the absorptive substrate and, with that, do not lead to the desired adhesion in the region of the bonded surface.
On the other hand, the investigations of the inventors have shown that the two-component mortar compositions, which are known from DE 41 31 457 A1 and contain acetoacetoxyalkyl (meth)acrylates as reactive diluents, do not exhibit satisfactory adhesion values, if they are used on concrete instead of on brick substrates. He also there is evidently interference with the curing in the region of the boundary layer between the mortar composition and the substrate.
It therefore follows from the state of the art that two-component mortar compositions for the chemical fastening technique, due to the combination of reactive resin, filler and auxiliary materials, exhibit a flow, wetting and adhesion behavior, which can be optimized only for a specific substrate and results in significantly inferior adhesion on other substrates. Consequently, for producing a two-component mortar composition, which has a balanced performance on all conventional mineral substrates, it had to be assumed that it is necessary to make compromises, as a result of which this performance level is clearly lower than the performance level of mortar compositions, which had been optimized especially for a particular substrate.
It was therefore to be expected that, if the reactive diluents, known from the state-of-the-art, are combined for different fastening bases, mortar compositions would be obtained, which would not ensure satisfactory adhesion on any of the substrates mentioned. On the other hand, two-component mortar compositions which do not contain such reactive diluents, would achieve an adhesion, which does not do justice to the requirements raised and, in no case, would reach the performance of mortar compositions, which had been optimized for the specific substrates.
Surprisingly, it has now turned out that the object, on which the present invention is based, can be accomplished owing to the fact that a reactive diluent mixture of at least one hydroxyalkyl (meth)acrylate and at least one acetoacetoxyalkyl (meth)acrylate is used in a two-component mortar composition of the type given above.